Fairbairn U.S. Pat. No. 4,004,042 is concerned with applying a wear and impact resistant coating by plasma-spraying tungsten carbide and nickel chrome boron powders onto a base metal. The coating is covered by a layer of nitrogen carried boric acid which forms a glossy protective film. The coating is then fused.
McCormick U.S. Pat. No. 4,024,617 is directed to applying a refractory coating to a ferrous metal substrate by providing a bonding element, such as nickel, at the interface and induction heating the coated substrate to the diffusion temperature.
A corrosion-resistant metal article is achieved by Gupta et al in U.S. Pat. No. 4,145,481 by applying ductile metal overlays. Porosity is limited by heating and applying isostatic pressure.